What is it?
Come on. You've heard of it. The manga started in 1991, written and illustrated by Naoko Takeuchi (who's apparently married to the author of Hunter x Hunter, but that's a rabbit hole for another time).
The first anime adaptation started in 1992, directed by several people through its long run:
- Satou Junichi (Junkers Come Here, Princess Tutu, Aria the Animation)
- Staring in 1994, Kunihiko Ikuhara
- From 1996 til the end in 1997, Takuya Igarashi (Ojamajo Doremi, Ashita no Nadja, Ouran High School Host Club)
Furthermore, there's been a host of stage musicals, live action dramas, and a second anime adaptation in 2014. Also a buttload of video games. (I play Jupiter and Merc in Jougai Rantou, btw.)
How's it connect to other stuff?
Via staff
Via its three directors,
Princess Tutu
Revolutionary Girl Utena
Ouran High School Host Club
Via influence
It's hard for a magical girl story, especially an action focused one like this, to not trace its roots back to Princess Knight in some way or another.